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Message: <blockquote data-quote="Cluster" data-source="post: 2855679" data-attributes="member: 105217">I have had and returned a few problem binoculars recently. when trying to describe the problem, I wonder if I could have used better terminology to describe the problem. These faults have included alignment, focus area differences (sweet-spot), mechanical problems in the focus and two kinds of dioptre problems.  It's one of the dioptre problems that have caused me some problem in trying to describe (although when returned to a proper binocular dealer/distributor, they should get my meaning perhaps). The first, mainly only seen on cheap bins, is where the dioptre requires re-adjustment for near focus (~3m) and far (>30m).  I guess that this is self explanatory. The second is more of a problem and is present on several of my binoculars.  This is where, after setting up the dioptre, I notice that when re-focussing on the same object the dioptre adjustment is off again. Careful investigation reveals that any dioptre adjustment is only good for when the focus is reached from a particular direction, say from near to far or from far to near.  I guess that, in these cases there is some drag or stiffness within the focussing mechanics for one barrel, so that one always lags the other..................The only way to use a binocular with this fault is to get used to arriving at the final focus from the same direction each time, more difficult than you might imagine.....Is there a commonly accepted/known short description for this "coming or going" focus fault?   Dave.</blockquote>

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